1. Field of the Invention
This invention relates to a coulter adjusting device for a reversible plow, and particularly to a coulter adjusting device for a reversible plow in which a coulter fixed to a mast frame side is swingable (i.e., movable angularly) and/or movable in a plowing width direction in accordance with variation in the plowing depth or the tread of a tractor for hauling the reversible plow.
2. Description of Related Art
A bottom plowing machine is conventionally used as one type of agricultural machine for performing plowing. In order to perform plowing of a field using the bottom plowing machine, the bottom plowing machine is hauled by a tractor while a bottom of the bottom plowing machine plows the soil with a predetermined plowing depth. In the conventional bottom plowing machine, during the plowing operation, the soil (i.e., conglomerate clay) is plowed up (scraped out) by the bottom to form a groove and the plowed-up soil is placed at only the right side of the groove with respect to a plowing direction while the plowing machine is reversed. After one groove is formed, the tractor is turned on a headland, and then the above operation is repeated to form the next groove. Therefore, to perform plowing with the conventional bottom plowing machine, an opening (i.e., grooving) operation must be performed at a central portion of a field (i.e., several portions of the field when the field is wide) initially, and then a predetermined plowing operation in accordance with a plowing manner is carried out. As a result, in the plowed field, the reversely scraped-out soil is piled symmetrically with respect to the groove which is formed during the plowing operation. Therefore, plowing and preparation of the field takes a long time, and the headland must be plowed up and the plowed-up soil is reversely piled up at the last stage, so that the conventional bottom plowing machine has poor working efficiency.
Recognizing that the working efficiency could be improved if plowing is continuously carried out, a reversible plowing machine has been recently proposed which has bottoms at upper and lower sides of a bottom frame. In a plowing operation using the reversible plowing machine, the tractor is turned on a headland after plowing one line on a field (that is, one groove is formed), and then the bottoms at the upper and lower sides are reversed to plow an unplowed line adjacent the plowed line. Therefore, a continuous plowing operation can be carried out using the reversible plowing machine by intermittently reversing the bottoms.
The reversible plowing machine comprises a reversible plow frame to which bottoms are secured, a non-reversible mast frame which is linked to a tractor through a three-point link, and coulters each provided in correspondence with each bottom and which serve to cut the soil. In a conventional bottom plowing machine using fixed or non-reversible bottoms, each of the coulters is fixedly disposed in front of each corresponding bottom in a plowing direction because the bottom itself is fixed or non-reversible. Accordingly, a problem occurs in the positioning of the coulters.
As the simplest means of solving this problem, a reversible bottom plowing machine as shown in FIG. 16 may be employed. As shown in FIG. 16, all coulters 1a, 2a, 3a, and 4a which are assigned to bottoms 1, 2, 3 and 4, respectively, are secured to a plow frame 5 so as to be rotatable together with the plow frame 5 relative to a non-reversible front frame 7 by extending and contracting a reversing cylinder 6. This machine has no problem in construction as compared to the system above, but has a problem in the driving force for plowing. That is, the plowing machine having the construction as described above has an extremely long body at the rear side of a cross bar, and thus a point of application of force against tractive resistance for the plowing is excessively deviated to a rear side, so that the tractor's driving force is ineffectively used.
In order to overcome the above disadvantages, a first coulter which is assigned to a first bottom (i.e., nearest to the tractor) is fixedly secured to a mast frame serving as a non-reversible or fixed member. However, a plow width (defined as the width of an area to be plowed in a plowing operation for one line) is unintentionally varied due to inclination of a tractor which is also varied in accordance with a plow depth (defined as the depth of the area to be plowed), so that the position of the coulters must be adjusted in a width direction of the plowing in correspondence with a reversing operation of the bottoms.
Further, in a tractor having a prescribed tread, a first coulter is frequently not disposed in front of a corresponding first bottom after the reversing operation of the bottoms. That is, the disposed position of the coulter in the reversing operation is dependent on the tractor tire tread. Accordingly, the position of the coulters must also be adjusted in the width direction in accordance with the tractor tread. To meet such a requirement, the plowing machine is mechanically more complicated.
In order to solve the problem in the position adjustment of the coulters, the same applicant has previously proposed two types of coulter adjusting devices as disclosed in Japanese Post-Examined Publication Nos. 61-25321 and 1-59841, respectively.
According to the coulter adjusting device as described above, the adjustment of offset and inclination of the coulters which are caused by a reversing operation of the bottoms can be performed by effectively using the property of the reversible plow machine. However, conventionally this adjustment has been manually carried out by the operator, and thus the adjustment operation is relatively cumbersome.